PROPERTIES OF A FUNGAL LACTASE

LACTASE is the common name for many P-galactosidases, E.C.3.2.1.23, the enzymes which hydrolyze fl-galactosidic bonds such as the one present in lactose. In the latter case, glucose and galactose are the end products of the reaction, but higher oligosaccharides may also be formed due to transgalactosidic activities (Aronson, 1952). Lactases have been identified in many tissues and cells of vegetable or animal origin. In microorganisms they have been found in various bacterial species (Cohn, 1957; Tacquet et al., 1966; Rohlfing and Crawford, 1966a, b; Anema, 1964), mycobacteria (Citti et al., 1965), Neurospora crassa (Lester and Byers, 1965), Aspergillus oryzae (Neuberg and Rosenthal, 1924), and Saccharomyces fragilis (Caputto et al., 1948; Szabo and Davies, 1964). Lactase, mainly the S. fragilis enzyme, has been suggested for many practical uses, all based on the conversion of lactose into a mixture of glucose and galactose. Lactose is less soluble than its hydrolytic products, glucose and galactose. Examples are the addition of lactose or milk products in bread making (Pomeranz et al., 1962; Pomeranz and Miller, 1963), increasing the milk solids in ice cream (Sampey and Neubeck, 1955), decreasing the thickening during storage of frozen concentrated milk products (Stimpson, 19.54), improving animal feeds (Stimpson, 1957). This paper reports on the rather different properties of a fungal lactase obtained from a mutant strain of Aspergillus foetidus.